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Procurement of raw materials ① Pressure vessel manufacturers should establish procurement control procedures for raw materials (such as sheets, pipes, welding materials, forgings, rods, and other materials used for pressure-bearing components) as well as purchased components. This control procedure should ensure that the pressure vessel materials used meet the specified requirements through methods such as inspecting, evaluating, and tracking the material suppliers. ②Material procurement is the primary step in material quality control. The pressure vessel manufacturing unit shall prepare procurement technical documents, which shall specify clearly the grade, specifications, material standards, technical ordering agreements, and quantity of the materials. Material procurement shall be carried out in accordance with the requirements of the procurement technical documents. ③ The ordering agreement for the material must comply with the relevant standards and design documents; where necessary, the smelting method, chemical composition, delivery condition, and any special requirements should all be specified in the agreement. ④When placing orders with overseas material manufacturers, it is necessary to meet the basic safety requirements stipulated in China’s Fixed Pressure Vessels Regulations as well as the specific requirements for manufacturing pressure vessels. ⑤The substitution of materials for stressed components must be approved in writing by the original design party in advance. Inspection of raw materials upon arrival at the factory – Principles for inspection upon arrival: ① The pressure vessel manufacturer should establish inspection and control procedures for raw materials (such as sheets, pipes, welding materials, forgings, rods, and other materials used in pressure-bearing components) as well as purchased components. ②The quality, specifications, and marking of the materials used for pressure vessels shall comply with the corresponding material standards specified in the design documents as well as the requirements of the order technical agreement. ③The manufacturers of steel plates specifically designed for pressure vessels must obtain the corresponding manufacturing license for special equipment. ④The pressure vessel manufacturing unit shall be responsible for the authenticity and consistency of the pressure vessel materials obtained as well as the material quality certificates. ⑤Materials with foreign brand names shall be those that are permitted for use according to the current foreign standards and specifications for pressure vessels, and for which there are existing instances of use abroad; their scope of application shall comply with the provisions of the corresponding foreign product standards. Upon arrival at the factory, steel plates, copper pipes, steel forgings, and steel bars are subject to inspection. Strict control over the materials used for the pressure-bearing components of pressure vessels is essential to ensure their quality, and this is a crucial measure for guaranteeing the quality of such vessels. Therefore, pressure vessel manufacturers should establish appropriate inspection systems to prevent substandard raw materials from reaching the production process. ①When raw materials arrive at the factory, the material inspector shall review the quality certificates in accordance with the requirements of the drawings, procurement technical documents, and material standards. The content of these certificates must be complete and thorough. The inspector checks the material’s grade, specifications, quantity, supply condition, inspection items and data, as well as the applicable standards, and the person responsible for material quality control assigns a material inspection number. a. The material quality certificate shall be the original issued by the steel mill, or a copy stamped with the steel mill’s quality inspection seal, as well as the inspection seal of the material supplier and the valid signature of the responsible person; b. Once it is confirmed that the material quality certificate meets the requirements, it is necessary to verify that the details on the certificate correspond to those of the actual material – that is, the batch number of the material, its grade, specifications, condition at the time of supply, and any markings on the material must all match those stated in the certificate; c. For special materials used in pressure vessels for which manufacturing permits are required, the quality certificate and the markings on the material must also include the manufacturing permit symbol and the permit number. ②After the material quality certificate has been approved upon inspection, the material inspector must verify the consistency between the quality certificate and the actual material. The markings on the actual material must be clear, and the grade, specifications, furnace batch number, and supply status must match those indicated on the quality certificate. ③The raw materials also need to be inspected: a. Visual quality. The surface of the material is free from defects such as cracks, bubbles, scars, folds, and inclusions. b. Specifications and geometric dimensions of the material. c. For all raw materials requiring re-inspection, such re-inspection shall be carried out in accordance with the project requirements. ④The manufacturer shall refuse to accept into stock raw materials that lack quality certificates, have no original markings, have quality certificates that do not match the raw materials, or fail re-inspection. ⑤When there are doubts regarding the material of the main stressed components, the person responsible for material quality control decides on the retesting requirements. ⑥Raw materials that have passed the inspection should be stored in the designated area according to their grade and specifications; stainless steel and carbon steel should be kept separately. The material supervisor is required to apply markings on the materials as specified, and these markings must be verified by the inspection personnel. ⑦Stainless steel and non-ferrous metal materials should be stored in dedicated areas and must not be left exposed outdoors. ⑧Keep proper records of material receipt inspection. ⑨The raw material reports that pass the above tests must be reviewed and approved by the person responsible for material quality control. Acceptance of welding materials: The quality of the weld joints between the pressure-bearing components of pressure vessel products represents a relatively weak link in terms of the safety of such vessels. Although the factors affecting the quality of welded joints are complex, the primary factor for ensuring their quality is to guarantee that the welding materials are of suitable quality, and to avoid using or mixing different welding materials during construction. ①Pressure vessel manufacturing units shall establish and strictly implement systems for the acceptance, retesting, storage, drying, distribution, and recycling of welding materials. ②The welding materials used to manufacture the pressure-bearing components of pressure vessels must ensure that the mechanical properties of the weld metal are higher than or equal to the specified limits for the base material. ③Upon the arrival of the welding materials at the factory, the purchasing staff, together with the person responsible for material quality control, examines whether the items and data listed in the material certification meet the relevant standards, as well as the requirements specified in the purchase order, technical specifications, and any special conditions. Upon passing the inspection, the material quality control officer assigns a welding material inspection number. ④Welding materials must come with quality certificates and clear, durable markings, and their packaging must be intact. ⑤After the welding material quality certificate passes the inspection, the purchasing officer, together with the material supervisor, verifies the batch number, weight, quantity, and other details of the actual welding materials against the quality certificate, ensuring that the information matches. ⑥Any tests that require special re-inspection procedures must be carried out as specified. ⑦Welding materials that have passed inspection and re-inspection should be stored in a weld material warehouse that meets management requirements, with the storage supervisor marking the materials in a visible location. ⑧The welding material storage area where welding materials are kept must meet the following conditions: a. Humidity meters should be installed in the primary and secondary welding material storage areas, and dehumidification devices should be provided. The temperature inside the warehouse should be above 5°C; the relative humidity should be below 60%. b. The keeper shall record the temperature and humidity in the welding materials storage twice a day, once in the morning and once in the afternoon. c. Harmful substances such as oils and water are strictly prohibited from being stored in the welding material warehouse. d. When distributing welding materials, those that were stored first should be issued first, to prevent them from remaining in storage for too long. e. Special welding materials should be kept by a designated person and stored in a separate area to prevent mixing. Inspection upon arrival of purchased and outsourced components: The inspection of purchased components (safety accessories, standard parts, etc.) is carried out in accordance with the principles applicable to raw materials. As for other metal materials used in the pressure vessel’s pressure-bearing elements, they are inspected following those same principles. However, safety accessories for pressure vessels (safety valves, rupture disc devices, emergency shut-off valves, pressure gauges, level gauges, temperature measuring instruments, etc.) as well as other auxiliary components (standard parts, gaskets, etc.) must be inspected in compliance with the technical specifications and relevant standards. (1) Safety accessories ① Upon the arrival of the safety accessories at the factory, the purchasing staff, together with the warehouse keeper and inspection personnel, will examine the contents of the quality certificate, as well as the model, specifications, scope of application, material used, applicable standards, and whether they meet the requirements specified in the order technical agreement. ② After the quality certificate confirms compliance, the markings, labels, and dimensional specifications of the actual product are verified in accordance with the quality certificate. ③ For safety accessories that still require verification, such verification shall be carried out after the above inspection tasks are completed successfully; once the verification is successful, they will be stored in inventory. (2) Other auxiliary materials ① Standard components for pressure vessels; if there are specific technical requirements, a quality certificate shall be provided. The content of the quality certificate must meet the technical requirements, and the markings must be clear; those with unclear markings will be rejected from entry into the database. ② For standard parts with specified performance requirements, there must be corresponding **marks as required by the standards; those with unclear marks will be rejected from entry. Inspection of outsourced components upon arrival: The outsourced processing of pressure vessel components is generally carried out by the pressure vessel manufacturing unit itself, either due to insufficient processing capabilities or because of time constraints in production. For outsourced processing, work is generally carried out on the material already provided; therefore, an agreement should be signed with the outsourcing party to clarify the scope of work, requirements, quality standards, and respective responsibilities. Alternatively, the construction drawings and processing specifications can be handed over to the outsourcing party along with the raw material for processing. Once the outsourced parts are completed and delivered to the factory, they should be inspected in accordance with the following principles. (1) Acceptance of stamped and hot-worked parts: Stamped and hot-worked parts refer to those components that are formed by pressure processing or other hot-working methods carried out by external contractors. ① Whether it is in line with the contents of the drawings, technical agreements, or processing requirements. ② Inspect the physical appearance quality and dimensions of stamped and hot-worked parts in accordance with drawings and other specifications. ③ During inspection, check whether the material markings are the original ones of the company (for outsourced parts that require markings, it should be required that the outsourcing party retain the original markings). If the outsourcing party is unable to retain the original markings, marking transfer should be carried out, and this must be confirmed by the inspection personnel from the outsourcing party, in order to prevent mix-ups of materials. (2) Inspection of heat-treated parts upon arrival at the factory ① After the heat-treated parts arrive at the factory, the subcontractors, together with the inspection staff, verify the automatic recording curves of heat treatment against the specified heat treatment procedures: checking whether the temperature at entry into the furnace, the rate of temperature increase, the holding time and temperature, the rate of temperature decrease, and the temperature upon exit from the furnace are all consistent. At the same time, the automatic recording paper for heat treatment curves should also include information such as the engineering number, part number, name, and quantity of the heat-treated part; the name and quantity of the test pieces processed along with it; the signatures of the operator and inspector; the date of heat treatment; and the inspection stamp of the heat treatment facility. ②Conduct a physical inspection to check whether there is any deformation during heat treatment and whether the sealing surface is protected. ③Heat treatment of specimens remaining in the furnace includes further heat treatment in the furnace, etc. (3) Inspection of mechanically processed outsourced parts upon arrival at the factory ①After the mechanically processed outsourced parts arrive at the factory, the personnel responsible for processing them, together with the inspection staff, examine the actual parts with regard to surface processing accuracy, dimensions, and tolerances, in accordance with the drawings and processing specifications. ②Whether the material markings have been clearly transferred. Acceptance of other metal materials; Acceptance of cast iron components. Since cast iron is a brittle material with low tensile strength, and its quality is greatly affected by the casting process, its use is restricted to the following areas: it cannot be used in pressure-bearing components of pressure vessels that contain media with extremely high, high, or toxic levels of hazard, nor in those vessels where the design pressure is 0.15 MPa or higher; it also cannot be used in pressure-bearing components of shell-and-tube waste heat boilers. In addition, the cast iron materials permitted for use in pressure vessels are specified in the ‘Regulations on Solid Pressure Vessels’. It is required that: ① Upon arrival of the cast iron components at the factory, the purchasing staff, together with the person in charge of material quality control, shall inspect the items guaranteed in the quality certificates, as well as the data, delivery condition, and grade, based on the drawings and technical agreements; the mechanical properties of such materials must meet the requirements of the relevant standards. ②The purchaser, together with the inspector, shall check the actual dimensions of the goods; there shall be no defects such as shrinkage cavities, slag inclusions, or porosity that could affect strength or processing quality. Acceptance of non-ferrous metal materials for pressure vessels ① The acceptance of non-ferrous metal materials (aluminum, iron, copper, nickel, and their alloys) used for pressure vessels is carried out in accordance with the principles applicable to the acceptance of raw materials. For special projects, the quality certificates must be verified in accordance with the requirements of the ordering technical agreement, and the actual products must be re-inspected. ②Non-ferrous metals used for pressure vessels should be stored in a dedicated area, with strict storage procedures in place; they must be kept separate from carbon steel and low-alloy steel. ③When ferrous and ferroalloy materials, nickel and nickel alloys, copper and copper alloys, aluminum and aluminum alloys, as well as tantalum, zirconium, niobium and their alloys are used as pressure-bearing components in pressure vessels, their design pressure, design temperature, and heat treatment conditions must comply with the relevant provisions of the Code for Pressure Vessels. Acceptance of composite steel plate materials for pressure vessels ① The acceptance of composite steel plates for pressure vessels upon arrival at the factory is carried out in accordance with the requirements for such raw materials. ②Composite steel plates for pressure vessels shall comply with the relevant provisions of the Code for Pressure Vessels. a. The shear strength at the composite interface of stainless steel-steel, nickel-steel, iron-steel, and copper-steel composite sheets, as well as the condition of the base material, shall comply with the provisions of the Solid Content Regulations. b. Carbon steel and low-alloy steel base materials (including steel plates and steel forgings) are subjected to impact tests in accordance with the specifications for base material standards. Acceptance of materials with foreign brand names ① The technical requirements for materials with foreign brand names shall not be lower than those of similar domestic brand name materials (such as phosphorus and sulfur content, the sampling location and direction for impact test specimens as well as the impact energy criteria, elongation after fracture, etc.). ②The material quality certificates and material markings shall comply with the provisions of the Solid Waste Regulations. ③Inspect the materials entering the factory and their quality certificates, and conduct verification tests on the chemical composition and mechanical properties of the materials. ④For materials used in welded structural compression members, a welding procedure qualification shall be carried out prior to first use. ⑤Steel materials with a minimum standard tensile strength of 540 MPa or higher, as well as low-alloy steel materials used at design temperatures below -40°C, shall undergo technical evaluation in accordance with the Solid Content Regulations. ⑥Materials of foreign brand names manufactured within the country must meet the requirements outlined in ① to ⑤ above, and they must also pass a technical review in accordance with the requirements of the Solid Waste Regulations. Reinspection of materials – General requirements for reinspection: ① Materials shall be reinspected in the following situations: a. When used to manufacture grade 4 forgings for category III pressure vessels; b. For materials of major pressure-bearing components whose quality certificates cannot be verified or regarding which there are doubts regarding their properties and chemical composition; c. For materials of foreign grades used to manufacture pressure-bearing components; d. For austenitic stainless steel flat plates used to manufacture major pressure-bearing components (one set of reinspection samples shall be taken from each end of the flat plate); e. For materials for which reinspection is required according to the design specifications. ②Re-inspection items and quantity: a. Surface quality of steel plates and material markings ； b. Austenitic stainless steel flat plates shall have their mechanical properties retested by batch number, while other materials shall have their chemical composition retested by furnace number and their mechanical properties retested by batch number ； c. When no ultrasonic testing certificate is provided, re-ultrasonic testing shall be carried out in accordance with the requirements of the Solid and Pressure Vessel Regulations. ③The results of the re-inspection of materials shall comply with the provisions of the relevant material standards or the requirements of the design drawings. ④Welding electrodes for low-temperature vessels shall be retested in batches for the moisture content in the flux or the diffused hydrogen content in the deposited metal, with the testing methods following the corresponding welding electrode standards or technical requirements. Various materials are retested upon arrival at the factory depending on their manufacturing methods. Steels used for pressure vessels include carbon steel, low-alloy steel, high-alloy steel, steel suitable for low temperatures, steel suitable for medium temperatures, and composite steel plates, among others. The retesting method should vary depending on whether the material requires heat treatment to restore its properties during the manufacturing process. ①During the manufacturing of pressure vessels, the material does not undergo any thermal processes related to phase changes in its microstructure; therefore, no heat treatment to restore its properties is required. This represents a standard manufacturing process, and the raw materials used in this process must meet the requirements specified for purchased components. ②When the material undergoes thermal processes of microstructural phase transformation as well as heat treatment required to restore its properties during the manufacture of pressure vessels, specimens should be prepared from the heat-treated test pieces provided by the steel mill for retesting of mechanical properties. If necessary, heat-treated test pieces can be directly cut from the raw materials, and samples can be taken for testing after undergoing the thermal processes simulating the manufacturing process. The thickness of the specimen taken from the test piece is equal to the thickness of the steel plate; both the length and width of the specimen must be at least 3 times the thickness of the steel plate. The axis of the specimen should be located at a distance of 1/4 of the thickness from the surface of the test piece. The position of the specimen should be at a distance of at least the thickness of the test piece from each of its sides. The inspection items and quantities shall comply with the requirements specified in the drawings or technical conditions. ③The re-inspection of imported materials from abroad shall be carried out in accordance with the testing methods, acceptance requirements, as well as the form, dimensions, and processing requirements specified by the relevant norms and standards of the material’s country of production; the technical requirements for such materials must not be lower than those of corresponding domestic materials. Re-inspection is also carried out in accordance with this principle for foreign-grade materials produced by domestic material manufacturing units.